1. Field of the Invention
This invention relates to devices and methods for the direct application of chemical substances to selected plants at specific locations thereon.
2. Background Art
The conventional methods of applying chemical substances to vegetation is by spraying, sprinkling, or sowing highly diluted solutions or mixtures of the chemicals on the whole plant area. Such "broadcast" methods reduce the desired concentration on the specific plants to be treated, increase the cost of chemicals, require the handling and distribution of large volumes of diluents, and subject humans, animals, vegetation, and other objects far removed from the treatment area to the chemicals due to "vaporization," "drift" "translocation," or "leaching".
To avoid the difficulties associated with the broadcast methods, the individual application of chemicals has been made by hand and by mechanical devices to selected plants. Selective application has permitted the use of highly potent but relatively safe non-selective herbicides for the control of weeds and other undesirable vegetation. A preferred kind of non-selective herbicide is a 41% solution of isopropylamine salt of N-(phosphonomethyl) glicine, as further described in U.S. Pat. Nos. 3,799,758 and 4,405,531, and sold under the trademark "ROUNDUP" by the Monsanto Agricultural Company, St. Louis, Mo. 63167.
As disclosed in Laughlin U.S. Pat. No. 2,988,841, mechanical devices have been proposed for the direct application of chemical substances to selected plants at specific locations thereon. An applicator such as a brush or pad is traversed across the area of vegetation at a pre-selected height, speed and angle, so as to produce a treatment zone without affecting underlying vegetation. Such a mechanical device includes height controlling wheels and a push handle or tractive support, or applicator brushes or pads are adjustably mounted on a rake-like structure.
Mechanical devices for the direct application of chemical substances to plants have been manufactured and sold as attachments to tractors, trailers and other vehicles. Hardy et al. U.S. Pat. No. 4,187,638 discloses a rope wick applicator in the form of an elongated pipe having a number of exposed portions of wick protruding from the pipe at spaced locations. Similarly, an applicator has been manufactured and sold by Ex-Cell-O Corporation, Century Engineering Division, Cedar Rapids, Iowa 52401, in the form of an elongated pipe having its lower outer surface covered with a carpet fed with chemical solution. A herbicide wiper consisting of an enclosure containing a series of nozzles that discharges onto a rounded carpeted underside is marketed by the Apple Manufacturing Company, Fort Pierce, Fla. A roller-type applicator covered with a carpet is being sold by Bill D. Wilson, P.O. Box 25, Lutz, Fla. 33549. A variety of other wipers covered with soft materials have been used to apply solutions to vegetation. When "ROUNDUP" is applied with wiping-type applicators, the practice has been to use solutions containing 70-90% water.
My U.S. Pat. No. 4,908,981 discloses an applicator pad for the selective application of herbicide to weeds overgrowing the height of turfgrass. The pad is supported by a skid that slides on the turfgrass. The skid can be oriented to uplift horizontally extending weeds into the path of the applicator pad. The skid is also designed to raise the applicator pad above sections of high ground. Also disclosed are forward bars that divert foreign objects from the path of the applicator.
My related U.S. Pat. 4,965,960 discloses the use of hard, non-spongy, porous materials to provide uniform distribution and application of liquids to vegetation, rather than the soft materials previously used. In some cases, this porous material is used to distribute the liquid to another material that serves as the applicator. A form of porous plastic is used that is dimensionally-stable, durable, and highly abrasion resistant. This material can be readily cut, sawed and drilled to provide liquid distribution channels and various applicator shapes. The porous plastic can be welded and is easily glued to other materials.
Weed control is a problem in a wide variety of locations worldwide. Many millions of dollars and millions of hours are spent annually in controlling weeds. Weed control methods include mechanical mowing, scalping, deep-set vertical mowing, hand removal, hoeing, excavation, turning off irrigation, starvation by eliminating normal fertilization, and spraying or wiping with herbicides and other chemicals.
The eradication of weeds growing above valuable vegetation, such as crops, lawns and grazing lands, is particularly difficult to accomplish without damaging the desirable vegetation. Such weed control is especially difficult when the weeds are massive or growing in large clumps or patches. Methods of controlling such weeds include spraying the weed-infested area with selective herbicides. Also, wipers have been used to apply non-selective herbicides onto the portions of the weeds that extended well above underlying desirable vegetation; however, this method has not always proved to be satisfactory, due to the inability to apply sufficient herbicide to the weeds without having the herbicide drip onto and damage the underlying vegetation.
A practice often associated with weed control is that of limiting the vertical growth of grasses that are used as ground cover. The common method is to mechanically mow the area when either the weeds or the grasses or both become too tall. Mechanical mowing is carried out in maintaining areas such as lawns, playing fields, parks and airports, and in preventing soil erosion beside highways, in orchards, groves and vineyards, and elsewhere. Another method that is practiced on a limited scale in some locations is to "chemically mow" the vegetation by spraying it with a highly diluted solution of a growth-retarding herbicide. This method usually does not completely eliminate the weeds nor the need for mechanical mowing.
Another related practice is to eliminate all vegetation growing under trees, between rows of crops, and in other locations. In some cases, the undesired vegetation is removed by mechanical means such as plowing. Another common method is to spray the area to be treated with potent herbicides. This inefficient method is expensive and usually results in at least some damage to nearby valuable vegetation or its fruit. Herbicide wipers are also used to a limited extent, but these have not been accurate enough, and the wipers tend to become contaminated with dirt, which reacts with and reduces the effectiveness of products such as the "ROUNDUP" brand of herbicide.